Her Senate questionnaire lists dozens of her awards and honors, her letters to the editor of her college newspaper, her speeches and cases she handled as a prosecutor, a lawyer in private practice and, for the last 17 years, as a federal judge.

Yet as she moves through the confirmation process, Judge Sotomayor has explained very little about one facet of her legal life: Sotomayor & Associates, the solo law practice she ran out of her Brooklyn apartment for several years in the 1980s.

In her questionnaire, Judge Sotomayor says she was the “owner” of Sotomayor & Associates, which she described as a consulting business she operated on the side from 1983 to 1986. During this period, she also worked, first for the Manhattan district attorney’s office and then as a member of Pavia & Harcourt, a large firm in Manhattan.

As a single practitioner, she told the Senate, she had helped “family and friends in their real estate, business and estate planning decisions.” The only other thing she has said about the practice is that if her clients “required more substantial legal representation, I referred the matter to my firm, Pavia & Harcourt, or to others with appropriate expertise.”

The White House has described Ms. Sotomayor’s outside legal work as an informal practice, one that never required her to file legal documents or appear in court. She never incorporated Sotomayor & Associates or registered it as a business in Manhattan or Brooklyn, where she then lived, according to public records, though she was not required to do so.

Associates in the district attorney’s office and George M. Pavia, the senior partner of Pavia & Harcourt, said they did not recall that she had done outside legal work at the time. “It is news to me,” Mr. Pavia said. He said she likely cleared the outside work with her direct supervisor, who is now dead.

At the time she began her legal consulting work, Ms. Sotomayor was an assistant district attorney, going through a divorce and earning about half of what lawyers in private practice made.

White House communications officials said the judge no longer had copies of the tax returns that listed the income, and any deductions, that she attributed to her outside work. A White House spokeswoman said at one point that because of the considerable passage of time, Judge Sotomayor could not estimate how many people she had counseled or remember their names.

The White House later provided names of three clients: an independent insurance salesman, no longer alive, for whom she helped review contracts; a cousin for whom she prepared a divorce — although the filing came a few years after the judge said she had stopped her outside work — and a friend who sought help setting up his dry cleaning business. The friend, Ken Kinzer, is married to one of the judge’s close friends, Dawn Cardi. Ms. Cardi, a lawyer, said initially that she did not recall the judge operating an outside legal practice. But Ms. Cardi said she subsequently remembered her friend’s assistance, and recalled that she gave her a pocketbook in appreciation.

Ms. Sotomayor’s outside work was approved, she said through a spokesman, by the Manhattan district attorney’s office, which has a policy that governs such work. Although the White House said Judge Sotomayor earned income in 1983, a spokeswoman for the district attorney’s office, Alicia Maxey Greene, initially said that the office did not allow prosecutors to charge for outside work. Generally, they were only allowed to help friends and family for free on a case-by-case basis.

Several former members of the office said they remembered the policy as being quite clear. “We were expressly prohibited from having a law practice on the side,” said Katharine Law, a friend of the judge who worked with her at the time.

But District Attorney Robert M. Morgenthau said subsequently that his spokeswoman had been wrong and that the office had been quite liberal at the time in approving outside work by staff, even if they charged fees.

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The judge’s choice of the name Sotomayor & Associates is regarded by some legal ethicists as a confusing departure for someone generally regarded as meticulous about preparation and following the rules.

Stephen Gillers, professor of legal ethics at New York University Law School, said Judge Sotomayor’s use of the larger-sounding title was “inadvisable because it is inaccurate.” He noted that bar associations frown on the use of the term “and associates” by single practitioners. “She could have just said, ‘Law Offices of Sonia Sotomayor,’ ” he said.

Bar associations have held that the use of such a name can be misleading. But Mr. Gillers said that since Ms. Sotomayor never appears to have advertised or to have put the name on letterhead, it is a technical issue and not one likely to ever have been cited by a disciplinary committee in the New York State court system. But he said that if the panel had received a complaint about the name, it would have required her to change it.

White House officials disagreed that the use of the name was a misstep, and they offered a written analysis by Hal R. Lieberman, a former disciplinary committee chief counsel in New York.

“Neither bar opinions nor cases to date have held that it was misleading for a sole practitioner to use the name ‘and Associates’ in such private communications,” he wrote in an e-mail message. “In fact, in the early 1980s, no rule prohibited the use of ‘and Associates’ in these circumstances and the only authority regarding the use of ‘and Associates’ in an advertising context was advisory, not mandatory, and thus not readily enforceable.”

A White House spokesman, Ben LaBolt, said, “All of the clients were well aware of the limited services Judge Sotomayor could provide given the other positions she held.”

Mr. LaBolt said that Ms. Sotomayor came up with the name when she was filling out her tax returns. “It was necessary to list a name for the practice on her tax returns,” he said.

Tax experts say there was nothing in the law that requires a lawyer, or any other self-employed person, to create a corporate name to report income, or deductions, on the standard form, known as a Schedule C. Just one’s own name will do. But Mr. LaBolt pointed out that the 1983 copy of the form asked the filer to list his or her “business name.”

“Significant time was not spent in choosing a name,” he said.

A version of this article appears in print on , on Page A11 of the New York edition with the headline: Little Information Given About Solo Law Practice Run by Sotomayor in ’80s. Order Reprints|Today's Paper|Subscribe